Simple , cheap , portable inverter is poor?

[Gyro]

You are assuming the OP with go to the expense of a switch on their new inverter. Surly too it can be omitted as a needless expense?

It's not just the inverter, it's the switching within the appliance too.

[Zero999]

You are assuming the OP with go to the expense of a switch on their new inverter. Surly too it can be omitted as a needless expense?

It's not just the inverter, it's the switching within the appliance too.

Which is exactly what I'm talking about. If the switch in the appliance is rated to charge the filter capacitors, then breaking the circuit is the least of your worries. There are some cases when it's an issue such as heaters and universal motors, but was talking about switched mode power supplies and LED lighting in particular.

[Faringdon]

As discussed, we can do a current limited 300v psu, and another for -300v...and switch between the two, repeatedly, and they soft start so they come up slow each time they come up.
Then its AC.

A 300 V square wave will work for some things but anything with resistive heaters or universal motors run directly from the line will potentially overload due to the high RMS voltage, so you will want to add some dead time to avoid overloading those devices and have a correct RMS voltage.  Now you have a bog standard modified sine inverter.

Thanks, ill post a sim soon, i think its evident that its cheaper and simpler than any inverter...and also doesnt suffer the EMC problem discussed earlier.

Granted about certain motors not running with it...we would put a label on it saying "Not for that use".

There are , as you know, zillions of "mains plug"  loads that will run off the +300VDC, (or +300,-300,+300...etc)...at 50Hz , or 55Hz, or 10Hz, whatever.

[Zero999]

As discussed, we can do a current limited 300v psu, and another for -300v...and switch between the two, repeatedly, and they soft start so they come up slow each time they come up.
Then its AC.

You were on about 350V at the start. I've lost track.

Isn't it just easier to use a single supply and a full H-bridge?

That scheme also involves a differential voltage of 600V inside the appliance which is quite nasty, especially given the fact there will be big capacitors.

[Halcyon]

Even if we dont sell it for much less than current offerings, it doesnt matter, since all you need to do in UK
is "get into the market with a known and registered prescence as an electronics designer and manufacturer"......once you have achieved that,
you can then make massive money by importing electronics in for people from China (middle-manning)...because your status as an electronics
company makes people think you are knowledgeable enough to buy in their electronics from China for them, and you then take your mega-riches, middle man cut.

How do you think your "status" will hold-up when people realise you are just importing cheap, shitty (and possibly dangerous) electronics from China?

[Faringdon]

Isn't it just easier to use a single supply and a full H-bridge?

Thanks, that gives the aforementioned EMC situation

That scheme also involves a differential voltage of 600V inside the appliance which is quite nasty, especially given the fact there will be big capacitors.

Thanks, though the normal mains is -339Vpk to +339Vpk,  etc etc, so its not really any different.
The DC bus wont see the 600 or so volts as you know.

Regarding 350V or 300V, its not been totally decided yet, but am thinking of the lowest voltage that can be gotten away with,  300V sounds reasonable being that normal mains  is some 339vpk.

How do you think your "status" will hold-up when people realise you are just importing cheap, shitty (and possibly dangerous) electronics from China?

Thanks, i think it will hold up just fine, the vast majority of electronics in the West is from China anyway, and the best electronics engineers for power supplies are from China.

[Andy Chee]

These people can buy an existing 150W inverter in the marketplace today.

Thanks yes they can...but it can be done cheaper than that...it doesnt need to be an inverter...it can just be an SMPS which boosts 12V to 300V.

You need to put an actual number on the price of your cheap inverter.

Merely boasting about cheapness is not going to convince anyone to manufacture your product.

[Halcyon]

How do you think your "status" will hold-up when people realise you are just importing cheap, shitty (and possibly dangerous) electronics from China?

Thanks, i think it will hold up just fine, the vast majority of electronics in the West is from China anyway, and the best electronics engineers for power supplies are from China.

You only need to look as far as this forum, let alone the perception of the general population, to realise that Chinese products are generally regarded as garbage. I avoid them like the plague (for various reasons). Even my mother who has little concept of electronics and how things work is aware of this. You'll also find some of the best engineers in Taiwan, Australia, UK, USA, Germany...

[Faringdon]

Thanks, and BTW, the Flyback that produces 300V from 12V, wont need to go +300,-300.+300....etc...it will only need to go from +300v to 0V to +300V.... repeatedly, (small dead time at 0V) because that gives the periodic zero current  so that it doesnt have trouble with "DC fusing".
So no need for AC at all.....just DC pulsating....and use an cheap AC fuse, because current goes periodically  to zero Amps....every 10ms or so, or 20ms or so, whatever you want.
As you can see, this is far simpler than an inverter.

[ejeffrey]

How is what you are suggesting different from a "modified sine wave" inverter?

[Faringdon]

It doesnt have the aforementioned EMC problem that a 4FET inverter has.
Plus a single flyback is much cheaper than a 4FET inverter.